package day19;

import java.util.Scanner;

public class Main {
    public static int getNum(int num) {
        int sum = 0;
        while(num > 1) {
            sum += num /3;
            num = num / 3 + num % 3;
            if(num == 2) {
                sum++;
                break;
            }
        }
        return sum;
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            if(n == 0) return;
            System.out.println(getNum(n));
        }
    }
}